So i changed all the plugs last night over to the ACdelco iridiom plugs and put some dielectric grease in the boots. Started her up this mornig then drove her for about 65 miles, most of it was at about 60mph but some was stop and go city traffic. Not once did it kick a code for cylinder 3 misfire. It ran great, had good power and didnt hesitate on acceleration.
The only thing its still doing still is shaking during idle. The idle speed is staying steady but the whole motor in shaking, I dont want to say it's running rough because it isnt. RPM's at idle are steady and there is no misfire, hesistation, skip , stumble, anything. It's Just shaking the whole truck.
It has done this for a while, I just assumed it was due to the misfire. But now that the misfire seems to have been fixed , what is causeing the shaking?
Would a bad motor mount cause this?

 

Did you install an aftermarket cai?

 

all i did for the intake was to remove the resonator and put a straight peice of tubing in its place and I plumbed the vaccuum line back into it. Then i made a bigger opening where the airbox connects to the fender well and ran more tubing connecting it all to the airdam on top of the hood That was done years ago , well before the misfire started happening.
the misfire is only at idle, from what i have read on other forums and the GM bulletine is that this is the bad head problem. since it only occures at idle. the CEL light starts blinking during idle but as soon as i step on the gas and give it to her the light goes away.
I'm going to have my mechanic do a leak down test to confirm the problem, but he's pretty sure thats it. He said he seen a few come into the dealership with the same problems and it was the head, seeing as my vin falls into the bad batch, we dont have high hopes for it.
Its got 130k on it and the misfire started at about 120k, so i guess i have made it farther then most.
Assuming it is a head issue, I'm leaning towards a whole motor replacement instead of just the head. From what i have read from others, a new head is about $2,000 or more. I can buy a brand new 3.7 online for about the same price with free shipping. I dont see why that wouldnt be the better option.

 

Not sure the 3.5 & 3.7 is a plug and play option. due to the PCM and TCM programming. You may have to get the computers from a 3.7 and have them flashed.

 

I asked about the aftermarket cai for your concern on "engine shaking at idle" NOT misfire.

I can't keep up to your endless posts(post enough info to get to the point), do you currently have a misfire?

Which cylinder?

Only at idle?

You isolated the misfire to a specific cylinder?... plugs, coils, injectors are good? if so, it could be a valve issue(leak down will verify)

If so, try induction cleaning with a bottle of seafoam first. GL

 

HummerZ,,,
You never specified as to why you asked that question. as to my endless post.... try reading the entire thread or all of my post.
Yes i have a misfire,
cylinder 3 only,
yes only at idle,
plugs, injectors, coils, intake gasket, camshaft sensors, knock sensor, camshaft solenoid actuator, valve cover gasket ARE ALL NEW ( which you would have known had you actually read thru this thread)
Havent done a leak down test yet
yes my vin falls in the batch of bad heads,
did seamfoam no more then 3 months ago, all new parts where done after.
yes you have problems with not reading
yes i have posted PLENTY of info, which you would have known had you read all the thread and my post.

 

Yeah i assumed i would have to get the computer flashed.

 

I read alot, EVERYDAY I WORK, FIXING CARS PROPERLY, AND GET PAID GOOD, DOING WHAT I DO; I read tons of diagnostic info, repair info, tsb's, etc... I do NOT need to read anything you post, however I am here offering advice, for FREE!
You throw parts at your rig, I offer advice, for FREE, as to the specific parts to replace, that would correct the issue you have.
1 post you stated the misfire was gone, now you state the misfire occurs only at idle, on the #3.
3 times I posted to check compression on cylinder #3.
10 days later and you still haven't checked?
IT'S NOT THE HEAD CAUSING YOUR MISFIRE, depending on the leak down test results, it's the valve not seating properly, and yes, excessive carbon buildup could cause that, and a thorough induction cleaning could correct!

You could throw a $2,000.00 head at it, or replace a $10.00 valve. GL

 

i realize your offering advice for free. I appreciate that. But you dont need to be so smug about it. last i checked this was a forum to discuse things and help others. Not to barade people. If your going to be a ***** about it then maybe you shouldn't offer advise.
you said that I wasnt posting enough info and that i needed to get to the point.
I posted plenty of info and updated as things changed, in hopes that it would help others understand better as to what was going on. I understand that there could be carbon build up, I did what i could to try and get rid of it....seafoam, lucas cylinder head cleaner.
Yes at one point I thaught the misfire was gone but it came back shortly.
Yes you did say to check the compression, sorry I dont have time to run to my mechanic and have him do a leak down test. I have a very busy life running my resataurant and have also been moving. So i kinda needed my hummer to either help move or drive to work.
just because you throw out a piece of advise doesnt mean you need to discount everything somebody says until they do as you say...master. You being a mechanic doesn't make you the god of the forum.

 

Not being a "*****", just offering advice. I dislike people jumping to conclusions and the worst case scenario.

I've seen it all, happens all the time, people coming to my shop for a second opinion, because the previous shop skipped over the diagnostic part and went to the worst case.

I had a customer in the shop this week, 120k miles on a '07 ford f-150 5.4l, with a driveability issue. Driving at 50mph, the vehicle bucks/shakes/vibrates. The previous shop told this guy he needed a transmission rebuild $2500.00+... I performed diagnostics, and told the guy he needed new spark plugs, so I replaced them. Guess what, problem solved..

BTW, yesterday I installed a new tensioner, idler pulley, and gatorback belt on my rig, (picked up the gates tensioner, dorman idler, and goodyear belt on ebay for $56.75 for all 3, shipping included). Idler and tensioner were original, belt was aftermarket but not a GATORBACK.
After install, I let it idle for about 5 minutes, to make sure all was good.
I went to shutdown the engine and the check engine light was on, wtf?
I connected the scanner and sure enough I recieved a P0300.
Right away I went to the garage to get my induction equipment, however I was out of seafoam.
So I pulled the air intake hose between the air filter box, and engine, started the rig up, put a pedal depressor on the accelorator, just to get to 1500rpms, and I emptied a full can of intake cleaner, pulse spraying at the throttle body through the resonator, with a tube on the spray nozzle. As soon as the can was empty, I went and cleared the code I received from the maf sensor (for having the air intake tube disconnected after the maf sensor), and let it sit idling in my driveway for over an hour.
No codes returned.